The present invention relates generally to arrangements for preventing the movement of a gear and, more particularly, to gear locking mechanisms having jam prevention structures.
A wide variety of devices have been used to selectively prevent rotational movement of gears and lock against actuation of whatever application is driven by the gears. In general, such arrangements can be referred to as "safelock" systems. However, the environment where the safelock system is employed can restrict the availability of certain prior devices for that purpose.
For example, in an aircraft hydraulic, mechanical and/or electrical power sources can employ gears to transmit power or actuation force to a variety of applications. In addition to the positive lock and safety criterion of ground-based safelock systems, the aircraft environment requires the arrangement to be lightweight, compact in size, highly reliable over long periods of time and unusually rugged with respect to mechanical and thermal stresses. In addition, ease of maintenance and serviceability are important design considerations.
As a specific example, safelock systems have previously been used to prevent inadvertent actuation of weapons access doors on military aircraft. One such safelock system included a gear segment which was selectively rotatable into engagement with the carrier gear of a hydraulic motor. The gear segment was supported for axial movement in either direction (backward or forward with respect to the direction of travel of the gear teeth) along the rotational axis between a plurality of biasing springs by a cam and pin assembly. Such bi-directional axial motion was intended to reduce the incidence of jamming between the gear teeth and the teeth of the gear segment by permitting the gear segment to be self seating between the gear teeth.
To further prevent such jamming, the gear teeth and the teeth of the gear segment were modified to include a taper from the side upon which those teeth first engage. That taper was typically "two dimensional" in that it was directed both inwardly from the side and downwardly from the top of the teeth.
Unfortunately, such prior safelock devices were subject to undesirably high friction upon actuation and, thus, did not always perform optimally. Accordingly, it was previously suggested to replace the cam/pin assembly with a ball bearing assembly. Unfortunately, single or three ball sets proved insufficient to sustain the load requirements, and significantly reduce actuation friction. As a result, a multiple ball array, such as a helical ball spline, was proposed. While such an array permitted significantly lower actuation friction, reliability maintenance for longer periods of time required relubrication of the array, preferably at the interior and outwardly from the longitudinal axis of the array. It was found, however, that acceptable relubrication structures interfered with the use of prior bi-directional spring biasing structures.
Biasing for axial motion of the gear segment forward with respect to the jack gear was still feasible using the prior biasing structure with the relubrication structure, but there was insufficient room for the prior backward motion biasing structure without at least significantly enlarging the size of the safelock assembly and complicating serviceability. In general, the prior biasing structures included helical springs on either side of the gear segment to achieve axially backward and forward biasing. Where only axially forward biasing was used, a helical spring was mounted on one side of the gear segment.
Accordingly, it is an object of this invention to provide an improved safelock system, especially for use in efficiency conscious environments such as aircraft. Further objects include at least providing a safelock system:
A. requiring reduced actuation friction, PA1 B. having a long useful life, PA1 C. with a decreased tendency to jam, PA1 D. of minimal cost and dimension, and PA1 E. which is easy to maintain and service.
These objectives are attained by the provision of a safelock system having a self-seating gear segment rotatably mounted on a helical ball spline for bi-directional axial movement with respect to the gear teeth to be locked. A relubrication structure is provided to service the interior of the ball spline. The interlocking teeth are two-dimensionally tapered from the point of initial engagement. Diverse biasing structures acting on opposing sides of the gear segment are employed to facilitate the axial self-seating reaction of the gear segment after initial engagement with the gear to be locked.
Other objects, advantages and novel features of this invention will become readily apparent from the following drawings and detailed description of preferred embodiments.